21 Photos
Siderite
Chemical Formula	FeCO3
Species	Carbonates
Crystal System	Trigonal
Mohs Scale	3-4
Specific Gravity	3.96
Color	Pale yellow to tannish, grey, brown, green, red, black and sometimes nearly colorless
Streak	White
Luster	Vitreous, Silky, Pearly
Refractive Index	n = 1.875 n = 1.633
Diaphaneity	Translucent
Cleavage	PerfectPerfect on .
Fracture	Irregular/Uneven, Conchoidal
Crystal Habit：Tabular crystals, often curved - botryoidal to massive
Geological Setting：Most often found in bedded sedimentary deposits with a biological component, with shales, clays and coal beds - suggesting that the siderite is biogenically created under low-oxygen and low-Ph conditions. It is also found in metamorphosed sedimentary rocks as more massively crystalline material, as a primary gangue mineral in hydrothermal deposits, and in pegmatites, including nepheline syenite pegamtites; as bog deposits.

Siderite is also the name of a type of iron meteorite.

Siderite is a mineral composed of iron carbonate FeCO₃. It takes its name from the Greek word σ?δηρο? sideros, “iron”. It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus. Both magnesium and manganese commonly substitute for the iron.

Siderite has Mohs hardness of 3.75-4.25, a specific gravity of 3.96, a white streak and a vitreous lustre or pearly luster.

Its crystals belong to the hexagonal system, and are rhombohedral in shape, typically with curved and striated faces. It also occurs in masses. Color ranges from yellow to dark brown or black, the latter being due to the presence of manganese (sometimes called manganosiderite).

Siderite is commonly found in hydrothermal veins, and is associated with barite, fluorite, galena, and others. It is also a common diagenetic mineral in shales and sandstones, where it sometimes forms concretions. In sedimentary rocks, siderite commonly forms at shallow burial depths and its elemental composition is often related to the depositional environment of the enclosing sediments. In addition, a number of recent studies have used the oxygen isotopic composition of sphaerosiderite (a type associated with soils) as a proxy for the isotopic composition of meteoric water shortly after deposition.